Area Forecast Discussion
Issued by NWS Rapid City, SD

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000
FXUS63 KUNR 150508
AFDUNR

AREA FORECAST DISCUSSION FOR WESTERN SD AND NORTHEASTERN WY
NATIONAL WEATHER SERVICE RAPID CITY SD
1008 PM MST SUN DEC 14 2014

.UPDATE...
ISSUED AT 843 PM MST SUN DEC 14 2014

NOW GETTING REPORTS OF FZDZ/-FZRA IN NORTHWEST SD...SO WILL ISSUE
QUICK FREEZING RAIN ADVISORY FOR OVERNIGHT TO ACCOUNT.

UPDATE ISSUED AT 732 PM MST SUN DEC 14 2014

02Z SURFACE ANALYSIS HAD LOW OVER SOUTHWEST KS. WATER VAPOUR
SHOWED UPPER LOW SPINNING OVER THE SAME LOCATION. UPPER LOW FAIRLY
COMPACT AND VIGOROUS LOOKING. 00Z KUNR SOUNDING SHOWED THERE WAS
SOME DRY AIR TO OVERCOME BEFORE SATURATION. 00Z KBIS SOUNDING
SUGGESTS FZDZ POSSIBLE WITH ST FLOWING INTO THE CWA FROM THE
NORTH...BUT CALLS TO SPOTTERS INDICATE EITHER NO PRECIPITATION OR
SOME SNOW GRAINS...LIKE AT THE OFFICE CURRENTLY. SNOW GRAINS SHOW
UP AS VERY LIGHT RETURNS IN VCP31 ON KUDX RADAR. REGIONAL RADAR
LOOPS SHOWED RETURNS HEADING NORTHWEST INTO SOUTHWEST/SOUTH
CENTRAL SD. MODEL SOUNDINGS SUGGEST A PERIOD OF SLEET POSSIBLE
OVER SOUTH CENTRAL SD THROUGH ABOUT 09Z. -SN STARTING TO DEVELOP
OVER NORTHEAST WY. ALL ACTIVITY IS FAIRLY CLOSE TO WHAT PREVIOUS
FORECAST/GUIDANCE WAS SUGGESTING...BUT WILL ADD FALL RIVER COUNTY
TO THE ADVISORY GIVEN EXPECTED SNOW TOTALS. UPDATE TO ACCOUNT FOR
LATEST TRENDS/THOUGHTS SOON.

&&

.SHORT TERM...THIS EVENING THROUGH MONDAY NIGHT
ISSUED AT 249 PM MST SUN DEC 14 2014

UPPER LEVEL ANALYSIS HAS STRONG LOW PRESSURE CENTER MOVING OUT OF
NW NEW MEXICO INTO THE CENTRAL PLAINS...WITH BROAD LOW PRESSURE
TROF ACROSS THE CENTRAL AND NORTHERN ROCKIES. SKIES ARE CLOUDY
ACROSS THE AREA WITH THE EXCEPTION OF THE DOWNSLOPE REGION ACROSS
THE CENTRAL AND SOUTHERN BLACK HILLS...WHERE SOME SUN IS MAKING IT
TO THE SURFACE. AT THE SURFACE...LOW PRESSURE HAS MOVED INTO
EASTERN SOUTH DAKOTA WITH THE TRAILING COLD FRONT THROUGH CENTRAL
NEBRASKA. CANADIAN HIGH PRESSURE CONTINUES TO MOVE INTO THE AREA.
TEMPERATURES AT 2PM ARE IN THE 30S...WITH NORTHWEST WINDS OF 15 TO
30 MPH.

THE CLOSED UPPER LOW WILL STRENGTHEN AND MOVE NORTHEASTWARD INTO
KS/NE TONIGHT. TROWAL WILL STRETCH INTO SOUTH CENTRAL SD...AND
PRECIPITATION WILL EXPAND ACROSS THAT AREA. SREF/BUFKIT SOUNDINGS
INDICATE THE POSSIBILITY FOR FREEZING RAIN/SLEET TONIGHT FOR AREAS
OF SOUTH CENTRAL SD...PRECIP CHANGES TO ALL SNOW BY MONDAY MORNING.
DO NOT EXPECT WINDS TO DECREASE MUCH OVERNIGHT. LOWS WILL BE
MAINLY IN THE 20S...WITH SOME TEENS IN THE BLACK HILLS.

NORTHWEST WINDS WILL STRENGTHEN AGAIN ON MONDAY BEHIND THE
LOW...JUST BELOW ADVISORY CRITERIA. SNOW WILL CONTINUE THROUGH
THE DAY...GRADUALLY DECREASING FROM WEST TO EAST. STRONG WINDS
COMBINED WITH SNOW WILL PRODUCE BLOWING SNOW AND REDUCED
VISIBILITIES.

SNOW TOTALS THROUGH MONDAY AFTERNOON ARE 3-6 INCHES ACROSS
PORTIONS OF NORTHEAST WYOMING AND THE NORTHERN BLACK HILLS...AND
ALSO ACROSS SOUTH CENTRAL SD THROUGH SHANNON COUNTY. LOCALLY
HIGHER AMOUNTS ARE POSSIBLE. BETWEEN THESE AREAS...1-2 INCHES
SHOULD BE EXPECTED.

.LONG TERM...TUESDAY THROUGH SUNDAY
ISSUED AT 249 PM MST SUN DEC 14 2014

SPLIT FLOW PATTERN TO PERSIST THROUGH THE LONG TERM PERIOD. A
BRIEF BLOCK WILL OCCUR ON THE NORTHERN PLAINS PER SHORTWAVE
RIDGING ON THE CANADIAN PRAIRIE PROVINCES...DELAYING WARMER RETURN
FLOW A COUPLE DAYS. THIS WILL SUPPORT PERSISTENT EASTERLY UPSLOPE
FLOW AS A SFC HIGH CENTER SHIFTS EAST. HAVE CUT HIGHS TUE AND WED
FOR THIS...ESP ON THE SD PLAINS. DRY WX EXPECTED THROUGH THE
PERIOD GIVEN TROUGH RE-LOADING IN THE WESTERN CONUS.
HOWEVER...ANOTHER STRONG SOUTHERN PERIPHERY UPPER TROUGH WILL
EJECT OUT OF THE SW CONUS IN THE WED-FRI PERIOD. THIS SYSTEM HAS
BEEN ADVERTISED AT TIMES TO SKIRT SCENTRAL SD...SIMILAR TO TODAY/S
SYSTEM NOW ENTERING THE PLAINS. IF ANY NORTHERN STREAM IMPULSES
TEND TO PHASE WITH THIS SYSTEM...A TRACK FARTHER NW COULD BE
POSSIBLE...WHICH COULD BRING SOME CHANCES FOR SNOW TO SCENTRAL
AREAS. THIS SYSTEM WILL NOT HAVE NEARLY AS MUCH MOISTURE TO WORK
WITH AS THE CURRENT SYSTEM...ESP GIVEN A DEPARTING CP AIRMASS WITH
STOUT DRY WEDGE. HENCE...ANY SNOW AMOUNTS WOULD LIKELY BE
MARGINAL. TENDENCIES FOR ANOTHER STRONG WESTERN NOAM RIDGE ARE
PRESENT IN MEAN ENSEMBLES AND DETERMINISTIC SOLUTIONS PER ANOTHER
EXTENSION OF THE EAST ASIAN UPPER JET. THIS COULD SPELL MUCH
WARMER CONDITIONS FOR THE FOLLOWING WEEK IF THE RIDGE BIASES EAST
AS IT HAS IN THIS PATTERN. HOWEVER...CURRENT LONG RANGE ECMWF/GFS
RUNS SUPPORT A CLOSED LOW IN THE PACIFIC NEAR HAWAII WITH A
DOMINATE NORTHERN STREAM...UNCHARACTERISTIC OF THE CURRENT REGIME.
IT WILL BE INTERESTING TO SEE HOW THIS UNFOLDS.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z MONDAY NIGHT)
ISSUED AT 1005 PM MST SUN DEC 14 2014

WIDESPREAD IFR CIGS/VSBYS ARE EXPECTED ACROSS THE AREA THROUGH 18Z
MONDAY. -FZDZ/-FZRA OVER NORTHWEST SD WILL CHANGE TO -SN LATE
TONIGHT. -PL/-SN OVER SOUTH CENTRAL SD WILL CHANGE TO -SN
OVERNIGHT. -SN OVER NORTHEAST WY WILL CONTINUE TO DEVELOP. LIFR
CIGS/VSBYS EXPECTED WITH THE BEST SNOWFALL AREAS. CONDITIONS WILL
SLOWLY IMPROVE LATE MONDAY.

&&

.UNR WATCHES/WARNINGS/ADVISORIES...
SD...WINTER WEATHER ADVISORY UNTIL 11 AM MST MONDAY FOR SDZ024-025-
     072.

     WINTER WEATHER ADVISORY UNTIL 5 PM MST /6 PM CST/ MONDAY FOR
     SDZ027-041>044-046-047-049.

     FREEZING RAIN ADVISORY UNTIL 4 AM MST MONDAY FOR SDZ001-002-
     012>014-073.

WY...WINTER WEATHER ADVISORY UNTIL 11 AM MST MONDAY FOR WYZ054>057.

     FREEZING RAIN ADVISORY UNTIL 4 AM MST MONDAY FOR WYZ071.

&&

$$

UPDATE...HELGESON
SHORT TERM...15
LONG TERM...JC
AVIATION...HELGESON




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